The meeting is expected to take place on the sidelines of the planned "G-20" economic summit. The official confirms Mr. Obama has written to Medvedev indicating U.S. plans to deploy a missile defense system in Eastern Europe could, in the words of the official "be affected" if Russia works with the U.S. to prevent Iran from building long range missiles.
The official says the essence of the letter is, "If you cooperate with us in helping to deal with the Iranian threat...if the threat is no longer there, it will affect the missile defense project" planned for Poland and the Czech Republic.
The official notes the letter stops short of a quid pro quo on the missile issue. According to the official, the letter suggests "we can get there" on the missile issue but he adds, "We're a long way from getting there."
The official describes the Russians as "intrigued" by the new outreach from Mr. Obama.
Peter Maer is a CBS News White House correspondent.